From 6727dbd52a0c8ac85658ed43678eed1b53ee6407 Mon Sep 17 00:00:00 2001 From: Warren Hunt Date: Tue, 19 Nov 2013 22:11:09 +0000 Subject: [PATCH] Microsoft Record Layout: zero sized base after base with vbtbl fix Microsoft adds an extra byte of padding before laying out zero sized non-virtual bases if the non-virtual base before it contains a vbptr. This patch adds the same behavior to clang. Differential Revision: http://llvm-reviews.chandlerc.com/D2106 git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@195158 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/AST/RecordLayoutBuilder.cpp | 11 + ...s-x86-empty-base-after-base-with-vbptr.cpp | 216 ++++++++++++++++++ 2 files changed, 227 insertions(+) create mode 100644 test/Layout/ms-x86-empty-base-after-base-with-vbptr.cpp diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp index 524c3ba254..4390e66c8b 100644 --- a/lib/AST/RecordLayoutBuilder.cpp +++ b/lib/AST/RecordLayoutBuilder.cpp @@ -2017,6 +2017,8 @@ static bool isMsLayout(const RecordDecl* D) { // * If the last field is a non-zero length bitfield and we have any virtual // bases then some extra padding is added before the virtual bases for no // obvious reason. +// * When laying out empty non-virtual bases, an extra byte of padding is added +// if the non-virtual base before the empty non-virtual base has a vbptr. namespace { @@ -2141,6 +2143,8 @@ public: bool LastBaseWasEmpty; /// \brief Lets us know if we're in 64-bit mode bool Is64BitMode; + /// \brief True if the last non-virtual base has a vbptr. + bool LastNonVirtualBaseHasVBPtr; }; } // namespace @@ -2304,6 +2308,7 @@ void MicrosoftRecordLayoutBuilder::layoutNonVirtualBases(const CXXRecordDecl *RD) { LazyEmptyBase = 0; LastBaseWasEmpty = false; + LastNonVirtualBaseHasVBPtr = false; // Lay out the primary base first. if (PrimaryBase) @@ -2331,6 +2336,10 @@ MicrosoftRecordLayoutBuilder::layoutNonVirtualBase(const CXXRecordDecl *RD) { const ASTRecordLayout &LazyLayout = Context.getASTRecordLayout(LazyEmptyBase); Size = Size.RoundUpToAlignment(LazyLayout.getAlignment()); + // If the last non-virtual base has a vbptr we add a byte of padding for no + // obvious reason. + if (LastNonVirtualBaseHasVBPtr) + Size++; Bases.insert(std::make_pair(LazyEmptyBase, Size)); // Empty bases only consume space when followed by another empty base. if (RD && Layout->getNonVirtualSize().isZero()) { @@ -2338,6 +2347,7 @@ MicrosoftRecordLayoutBuilder::layoutNonVirtualBase(const CXXRecordDecl *RD) { Size++; } LazyEmptyBase = 0; + LastNonVirtualBaseHasVBPtr = false; } // RD is null when flushing the final lazy base. @@ -2356,6 +2366,7 @@ MicrosoftRecordLayoutBuilder::layoutNonVirtualBase(const CXXRecordDecl *RD) { // Note: we don't update alignment here because it was accounted // for during initalization. LastBaseWasEmpty = false; + LastNonVirtualBaseHasVBPtr = Layout->hasVBPtr(); } void MicrosoftRecordLayoutBuilder::layoutVBPtr(const CXXRecordDecl *RD) { diff --git a/test/Layout/ms-x86-empty-base-after-base-with-vbptr.cpp b/test/Layout/ms-x86-empty-base-after-base-with-vbptr.cpp new file mode 100644 index 0000000000..293a61b96e --- /dev/null +++ b/test/Layout/ms-x86-empty-base-after-base-with-vbptr.cpp @@ -0,0 +1,216 @@ +// RUN: %clang_cc1 -fno-rtti -emit-llvm-only -triple i686-pc-win32 -fdump-record-layouts -cxx-abi microsoft %s 2>/dev/null \ +// RUN: | FileCheck %s +// RUN: %clang_cc1 -fno-rtti -emit-llvm-only -triple x86_64-pc-win32 -fdump-record-layouts -cxx-abi microsoft %s 2>/dev/null \ +// RUN: | FileCheck %s -check-prefix CHECK-X64 + + +struct U { char a; }; +struct V { }; +struct W { }; +struct X : virtual V { char a; }; +struct Y : virtual V { char a; }; +struct Z : Y { }; + +struct A : X, W { char a; }; + +// CHECK: *** Dumping AST Record Layout +// CHECK: 0 | struct A +// CHECK: 0 | struct X (base) +// CHECK: 0 | (X vbtable pointer) +// CHECK: 4 | char a +// CHECK: 9 | struct W (base) (empty) +// CHECK: 9 | char a +// CHECK: 12 | struct V (virtual base) (empty) +// CHECK: | [sizeof=12, align=4 +// CHECK: | nvsize=12, nvalign=4] +// CHECK-X64: *** Dumping AST Record Layout +// CHECK-X64: 0 | struct A +// CHECK-X64: 0 | struct X (base) +// CHECK-X64: 0 | (X vbtable pointer) +// CHECK-X64: 8 | char a +// CHECK-X64: 17 | struct W (base) (empty) +// CHECK-X64: 17 | char a +// CHECK-X64: 24 | struct V (virtual base) (empty) +// CHECK-X64: | [sizeof=24, align=8 +// CHECK-X64: | nvsize=24, nvalign=8] + +struct B : X, U, W { char a; }; + +// CHECK: *** Dumping AST Record Layout +// CHECK: 0 | struct B +// CHECK: 0 | struct X (base) +// CHECK: 0 | (X vbtable pointer) +// CHECK: 4 | char a +// CHECK: 8 | struct U (base) +// CHECK: 8 | char a +// CHECK: 9 | struct W (base) (empty) +// CHECK: 9 | char a +// CHECK: 12 | struct V (virtual base) (empty) +// CHECK: | [sizeof=12, align=4 +// CHECK: | nvsize=12, nvalign=4] +// CHECK-X64: *** Dumping AST Record Layout +// CHECK-X64: 0 | struct B +// CHECK-X64: 0 | struct X (base) +// CHECK-X64: 0 | (X vbtable pointer) +// CHECK-X64: 8 | char a +// CHECK-X64: 16 | struct U (base) +// CHECK-X64: 16 | char a +// CHECK-X64: 17 | struct W (base) (empty) +// CHECK-X64: 17 | char a +// CHECK-X64: 24 | struct V (virtual base) (empty) +// CHECK-X64: | [sizeof=24, align=8 +// CHECK-X64: | nvsize=24, nvalign=8] + +struct C : X, V, W { char a; }; + +// CHECK: *** Dumping AST Record Layout +// CHECK: 0 | struct C +// CHECK: 0 | struct X (base) +// CHECK: 0 | (X vbtable pointer) +// CHECK: 4 | char a +// CHECK: 9 | struct V (base) (empty) +// CHECK: 10 | struct W (base) (empty) +// CHECK: 10 | char a +// CHECK: 12 | struct V (virtual base) (empty) +// CHECK: | [sizeof=12, align=4 +// CHECK: | nvsize=12, nvalign=4] +// CHECK-X64: *** Dumping AST Record Layout +// CHECK-X64: 0 | struct C +// CHECK-X64: 0 | struct X (base) +// CHECK-X64: 0 | (X vbtable pointer) +// CHECK-X64: 8 | char a +// CHECK-X64: 17 | struct V (base) (empty) +// CHECK-X64: 18 | struct W (base) (empty) +// CHECK-X64: 18 | char a +// CHECK-X64: 24 | struct V (virtual base) (empty) +// CHECK-X64: | [sizeof=24, align=8 +// CHECK-X64: | nvsize=24, nvalign=8] + +struct D : X, U, V, W { char a; }; + +// CHECK: *** Dumping AST Record Layout +// CHECK: 0 | struct D +// CHECK: 0 | struct X (base) +// CHECK: 0 | (X vbtable pointer) +// CHECK: 4 | char a +// CHECK: 8 | struct U (base) +// CHECK: 8 | char a +// CHECK: 9 | struct V (base) (empty) +// CHECK: 10 | struct W (base) (empty) +// CHECK: 10 | char a +// CHECK: 12 | struct V (virtual base) (empty) +// CHECK: | [sizeof=12, align=4 +// CHECK: | nvsize=12, nvalign=4] +// CHECK-X64: *** Dumping AST Record Layout +// CHECK-X64: 0 | struct D +// CHECK-X64: 0 | struct X (base) +// CHECK-X64: 0 | (X vbtable pointer) +// CHECK-X64: 8 | char a +// CHECK-X64: 16 | struct U (base) +// CHECK-X64: 16 | char a +// CHECK-X64: 17 | struct V (base) (empty) +// CHECK-X64: 18 | struct W (base) (empty) +// CHECK-X64: 18 | char a +// CHECK-X64: 24 | struct V (virtual base) (empty) +// CHECK-X64: | [sizeof=24, align=8 +// CHECK-X64: | nvsize=24, nvalign=8] + +struct E : X, U, Y, V, W { char a; }; + +// CHECK: *** Dumping AST Record Layout +// CHECK: 0 | struct E +// CHECK: 0 | struct X (base) +// CHECK: 0 | (X vbtable pointer) +// CHECK: 4 | char a +// CHECK: 8 | struct U (base) +// CHECK: 8 | char a +// CHECK: 12 | struct Y (base) +// CHECK: 12 | (Y vbtable pointer) +// CHECK: 16 | char a +// CHECK: 21 | struct V (base) (empty) +// CHECK: 22 | struct W (base) (empty) +// CHECK: 22 | char a +// CHECK: 24 | struct V (virtual base) (empty) +// CHECK: | [sizeof=24, align=4 +// CHECK: | nvsize=24, nvalign=4] +// CHECK-X64: *** Dumping AST Record Layout +// CHECK-X64: 0 | struct E +// CHECK-X64: 0 | struct X (base) +// CHECK-X64: 0 | (X vbtable pointer) +// CHECK-X64: 8 | char a +// CHECK-X64: 16 | struct U (base) +// CHECK-X64: 16 | char a +// CHECK-X64: 24 | struct Y (base) +// CHECK-X64: 24 | (Y vbtable pointer) +// CHECK-X64: 32 | char a +// CHECK-X64: 41 | struct V (base) (empty) +// CHECK-X64: 42 | struct W (base) (empty) +// CHECK-X64: 42 | char a +// CHECK-X64: 48 | struct V (virtual base) (empty) +// CHECK-X64: | [sizeof=48, align=8 +// CHECK-X64: | nvsize=48, nvalign=8] + +struct F : Z, W { char a; }; + +// CHECK: *** Dumping AST Record Layout +// CHECK: 0 | struct F +// CHECK: 0 | struct Z (base) +// CHECK: 0 | struct Y (base) +// CHECK: 0 | (Y vbtable pointer) +// CHECK: 4 | char a +// CHECK: 9 | struct W (base) (empty) +// CHECK: 9 | char a +// CHECK: 12 | struct V (virtual base) (empty) +// CHECK: | [sizeof=12, align=4 +// CHECK: | nvsize=12, nvalign=4] +// CHECK-X64: *** Dumping AST Record Layout +// CHECK-X64: 0 | struct F +// CHECK-X64: 0 | struct Z (base) +// CHECK-X64: 0 | struct Y (base) +// CHECK-X64: 0 | (Y vbtable pointer) +// CHECK-X64: 8 | char a +// CHECK-X64: 17 | struct W (base) (empty) +// CHECK-X64: 17 | char a +// CHECK-X64: 24 | struct V (virtual base) (empty) +// CHECK-X64: | [sizeof=24, align=8 +// CHECK-X64: | nvsize=24, nvalign=8] + +struct G : X, W, Y, V { char a; }; + +// CHECK: *** Dumping AST Record Layout +// CHECK: 0 | struct G +// CHECK: 0 | struct X (base) +// CHECK: 0 | (X vbtable pointer) +// CHECK: 4 | char a +// CHECK: 9 | struct W (base) (empty) +// CHECK: 12 | struct Y (base) +// CHECK: 12 | (Y vbtable pointer) +// CHECK: 16 | char a +// CHECK: 21 | struct V (base) (empty) +// CHECK: 21 | char a +// CHECK: 24 | struct V (virtual base) (empty) +// CHECK: | [sizeof=24, align=4 +// CHECK: | nvsize=24, nvalign=4] +// CHECK-X64: *** Dumping AST Record Layout +// CHECK-X64: 0 | struct G +// CHECK-X64: 0 | struct X (base) +// CHECK-X64: 0 | (X vbtable pointer) +// CHECK-X64: 8 | char a +// CHECK-X64: 17 | struct W (base) (empty) +// CHECK-X64: 24 | struct Y (base) +// CHECK-X64: 24 | (Y vbtable pointer) +// CHECK-X64: 32 | char a +// CHECK-X64: 41 | struct V (base) (empty) +// CHECK-X64: 41 | char a +// CHECK-X64: 48 | struct V (virtual base) (empty) +// CHECK-X64: | [sizeof=48, align=8 +// CHECK-X64: | nvsize=48, nvalign=8] + +int a[ +sizeof(A)+ +sizeof(B)+ +sizeof(C)+ +sizeof(D)+ +sizeof(E)+ +sizeof(F)+ +sizeof(G)]; -- 2.40.0